Method of making textile fiber



Patented Apr. 28, 1953 METHOD OF MAKING TEXTILE FIBER DRAFT ING' ELEMENTS Richard A. Garrett, Lancaster Township, Lancaster County, Pa., assignor to Armstrong Cork Company, Lancaster,

Pennsylvania N Drawing.

Pa., a corporation of Application September 29, 1950,

Serial No. 187,669. In Great Britain November 4 Claims.

This invention relates to a method of making textile fiber drafting elements and is concerned particularly with the production of roll covers or cots which are used in the drafting of cotton, rayon, worsted, and other fibers. Such cots are manufactured with a matrix of synthetic rubher and may include cork particles and other compounding ingredients. In the drafting of fibers, it has been found that a tendency exists for the fibers to lap up around the drafting roll, and the problem is particularly difficult in drafting rayon and similar fibers. This lapping tendency is present in roll covers formed from certain types of butadiene-acrylonitrile synthetic rubbers, such as the synthetic rubber of this type sold as "Perbunan or Paracril. This product is made by Standard Oil Company of New Jersey and contains 74% butadiene and 26% acrylonitrile. Other examples of butadiene-acrylonitrile synthetic rubbers which are deficient in lap resistance are two varieties of I-Iycar made by Goodrich Chemical Company and known as O. R. which contains 60% butadiene and 40% acrylonitrile and O. R. which contains 75% butadiene and 25% acrylonitrile, and certain varities of Chemigum manufactured by Goodyear Tile and Rubber Company, known as Chemigum N-3 which contains 60% butadiene and 40% acrylonitrile and Chemigum N-i which contains 70% butadiene and acrylonitrile.

The princi al object of the present invention is to improve the lap resistance of textile fiber drafting elements such as roll covers which employ a matrix of butadiene-acrylonitrile synthetic rubber which is normally deficient in lap resistance.

According to the present invention, the deficient synthetic rubber in an uncompounded condition is heated in the presence of oxygen while it is mechanically worked to expose substantially all of it to oxygen while in a heated condition for an interval sufficient to substantially improve the lap resistance of the synthetic rubber. Thereafter, the rubber is compounded and vulcanized in the usual manner.

As disclosed in Patents 2,450,409 and 2,450,410, the lap resistance of various synthetic rubbers can be improved by adding animal glue or other electrolyte thereto, and the present invention may be used in the preparation of roll covers ed, the type of mechanical working, the presence of anti-oxidants in the uncompounded synthetic rubber stock, and other variable factors. The interval of treatment will depend, in addition, upon the temperature to which the stock is elevated during mechanical working, higher tem peratures normally requiring shorter periods of time to effect the desired improvement in lap resistance. Overtreatment by excessive heating or from heating for a prolonged period results in a noticeable decrease in lap resistance and also tends to produce compounds which are diflicult to process because of increase in the nerve of the compound. Charring of the rubber or other deleterious action may also result from overtreatment. Also, as the temperature is increased the duration of the treatment decreases and becomes more difficult to control because the time factor is so short. It is preferred, therefore, to heat at temperatures below the critical upper limit and for a fairly substantial period of time to obtain optimum lap resistance and avoid deleterious action upon the synthetic rubber, at the same time providing for convenient control of the process. The temperature must be elevated substantially above normal mixing or milling temperatures in order to secure maximum lap resistance. The lower the temperature, generally, the longer the treatment period required to obtain maximum results.

The heat treatment effect is believed to be a combination time-and-temperature action; and there is believed to be some oxidation or other chemical reaction involved. for heat treatment in the absence of oxygen does not improve lap resistance of the synthetic rubber when compounded. It has been observed that the use of anti-oxidants beyond the normal small amount of anti-oxidant contained in the uncompounded synthetic rubber as supplied by the manufacturer tends to inhibit the effect of the heat treatment.

The heat treatment may be effected by processing the uncompounded synthetic rubber in a heated Banbury mixer or a heated two-roll rubber mill. As mentioned previously, a factor a'ffecting the final lap resistance of the product is the nature of the mechanical working or mastication of the uncompounded synthetic rubber. The results achieved by mechanically working on an open two-roll rubber mill will differ from those achieved by mastication in a Banbury mixer using the same temperature and period of treatment. It is believed that this difference may be due to the accessibility of the material to oxygen during the course of the mastication, this. of

3 course, being different in the case of the open mill than in a closed Banbury mixer.

The mechanical working should be accomplished for a period of time sufiicient to expose 4 to form roll covers and other textile fiber drafting elements. A specific example of a roll cover compound produced in accordance with the invention for fabrication into a cot or roll covering substantially all of the synthetic rubber to oxygen 5 is given below: while in a heated condition. Where there is sub- Parts by weight sequent mechanical working of the mass at a Perbunan (butadiene-acrylonitrile copolyhigh temperature; for example, when an electromer) heat treated in accordance with the lyte such as glue is mixed into the synthetic invention 100 rubber, as disclosed in the patents mentioned, it Sulphur 10 will not be necessary for the original heat treat- Triaoetin l0 ment to be as extensive as in the case where there Titanium dioxide is no subsequent high temperature working of Zinc oxide 10 the mass. Graphite No. 64 2.6 The maximum temperature of treatment of 15 Benzothiazyl disulphide 1.5 butadiene-acrylonitrile synthetic rubber on a Diphenylguanidine 0.2 commercial scale is about 375 F., and the mini- Glue 50 mum interval of treatment is about five minutes. The Perbunanv in the above example is pre- The mmtmum temPemture 15 about, 250 for pared by heat treatment in an open two-roll rubcomtnerclal production and the f f ber mill for twenty-five minutes at 275 F. Into Val 18 about fifty mlnutes. These times and inthis heat treated Perbunan is dispersed the tervals of treatment W111 vary as mentloned glue which has been water-softened and the mixaboveture is milled for ten-fifteen minutes at about The following are examples of the heat treat- 240 F. to drive off the moisture and obtain a ment of a Stock of uniform dispersion of the glue in the synthetic u c p u rubber in c ce W the rubber. The temperature is then reduced bepresent invention: fore the other compounding ingredients are addiitlttitrii M33235... fiiiiiitititt Lap Resistance OHM l 50 minutes at 250 F. open mill 10-l5n1ir1utesat 240 F Substantial improvement. 2 10 minutes at 275 F .do do Do. 3 25 minutes at 275 F do Maximum improvement. 4 25 minutes at 320 F -.do Do.

(This example sh ws that a more extensive original heat treatment is desirable if there is no subsequent high temperature milling step.)

25 minutes at 275 F Banbury mixer 25 minutes at 320 F .do

l0 15 minutes at 240 F. .do

Slight improvement. Maximum improvement.

(Longer times and higher temperatures than indicated above for maximum lap resistance tend to make the material less readily workable.)

The preferred temperature range is between about 250 F. and about 320 F., and the preferred interval of treatment is about twenty-five minutes. This provides a temperature range which is low enough to permit accurate control of the process. It also provides a reasonably short period of treatment which will not be burdensome in commercial practice. Where an open mill is employed, the optimum results appear to be achieved by heating at 275 F. for twenty-five minutes where there is subsequent milling for the addition of glue in the compounding of the stock. Where there is no subsequent high temperature milling, the heat treating of the uncompounded stock is effected at about 320 F. for optimum results. Where Banbury mixing is employed to effect the mechanical working of the uncompounded synthetic rubber, optimum results are achieved at 320 F., with a treating interval of twenty-five minutes where there is a subsequent milling for the addition of glue in the compounding of the stock.

Where it is possible to elevate the temperature of the mill rolls by the application of high pressure steam, temperatures in the order of 375 F. may be employed for a period of about five minutes. As mentioned above, when higher temperatures are employed, care must be exercised to avoid overtreatment.

The synthetic rubber which has been heat treated in accordance with the invention may be compounded with the usual ingredients, including an electrolyte such as glue, if desired,

ed in accordance with the general practice. The milled mass is fed to a tuber, and a body of approximately the desired diameter is formed and placed on a mandrel. The assembly is wrapped with cotton tape and vulcanized by the application of heat at about 300 F. for about one hour. The tube is then removed from the mandrel, cut to the desired lengths, and they are ready for application as covers for drafting rolls. The covers are buffed by grinding to produce a desired surface finish after they have been assembled on the rolls.

In the above example, sulphur is a vulcanizing agent, triacetin is a plasticizer, titanium dioxide and graphite are pigments, zinc oxide is a vulcanization promoter, and the benzothiazyl disulphide and diphenylguanidine are accelerators. The usual substitutions may be made for these ingredients, as is well known to the synthetic rubber compounder.

In the above example Perbunan has been used as the butadiene-acrylonitrile type synthetic rubber. Generally, similar results can be obtained by substituting other butadiene-acrylonitrile synthetic rubbers which are normally deficient in lap resistance. It is pointed out that some butadiene-acrylonitrile synthetic rubbers possess better lap resistance than others. Practice of the invention will improve those which are so deficient in their lap resistance as to be unsatisfactory for commercial use in services where lapping is a factor of major importance, as in rayon spinning. This applies regardless ofthe' particular proportioning of the butadiene and acrylonitrile components of the copolymer.

I claim:

1. In amethod of making textile fiber drafting elements employing a matrix of butadiene-acrylonitrile synthetic rubber which is deficient in lap resistance, the improvement which comprises heating said deficient synthetic rubber in an uncompounded condition to a temperature between 250 F. and 375 F. in the presence of oxygen while mechanically working the synthetic rubber to expose substantially all of it to oxygen while in a heated condition for an interval of between five and fifty minutes, sufiicient to substantially improve the lap resistance of said synthetic rubber, and thereafter compounding thesynthetic rubber so treated, forming the same into a textile fiber drafting element, and vulcanizing the same.

2. In a method of making textile fiber drafting elements employing a matrix of butadiene-acrylonitrile synthetic rubber which is deficient in lap resistance, the improvement which comprises heating said deficient synthetic rubber in an uncompounded condition to a temperature between 250 F, and 375 F. in the presence of oxygen while milling the synthetic rubber to expose substantially all of it to oxygen While in a heated condition for an interval of between five and fifty minutes, sufficient to substantially improve the lap resistance of said synthetic rubber, and thereafter compounding the synthetic rubber so treated, forming the same into a textile fiber drafting element, and vulcanizing the same.

3. In a method of making textile fiber drafting elements employing a matrix of butadiene-acrylonitrile synthetic rubber which is deficient in lap resistance, the improvement which comprises heating said deficient synthetic rubber in an un compounded condition to a temperature between 250 F. and 375 F. in the presence of oxygen while milling the synthetic rubber to expose substantially all of it to oxygen while in a heated condition for an interval of between five and fifty minutes, sufiicient to substantially improve the lap resistance of said synthetic rubber, thereafter compounding the synthetic rubber with an electrolyte while mechanically working the mass at a temperature in the order of 240 F, and subsequently forming the same into a textile fiber drafting element and vulcanizing the compounded heat-treated rubber.

4. In a method of making textile fiber drafting elements employing a matrix or butadiene-acrylonitrile synthetic rubber which is deficient in lap resistance, the improvement which comprises heating said deficient synthetic rubber in an uncompounded condition to a temperature of about 320 F. in the presence of oxygen while mechanically working the synthetic rubber to expose substantially all of it to oxygen while in a heated condition for an interval of about twenty-five minutes, sufficient to substantially improve the lap resistance of said synthetic rubber, and thereafter compounding the synthetic rubber so treated, forming the same into a textile fiber drafting element, and vulcanizing the same.

RICHARD A. GARRETT.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,450,410 Baymiller Oct. 5, 1948 2,505,349 Daly Apr. 25, 1950 

1. IN A METHOD OF MAKING TEXTILE FIBER DRAFTING ELEMENTS EMPLOYING A MATRIX OF BUTADIENE-ACRYLONITRILE SYNTHETIC RUBBER WHICH IS DEFICIENT IN LAP RESISTANCE, THE IMPROVEMENT WHICH COMPRISES HEATING SAID DEFICIENT SYNTHETIC RUBBER IN AN UNCOMPOUNDED CONDITION TO A TEMPERATURE BETWEEN 250* F. AND 375* F. IN THE PRESENCE OF OXYGEN WHILE MECHANICALLY WORKING THE SYNTHETIC RUBBER TO EXPOSE SUBSTANTIALLY ALL OF IT TO OXYGEN WHILE IN A HEATED CONDITION FOR AN INTERVAL OF BETWEEN FIVE AND FIFTY MINUTES, SUFFICIENT TO SUBSTANTIALLY IMPROVE THE LAP RESISTANCE OF SAID SYNTHETIC RUBBER, AND THEREAFTER COMPOUNDING THE SYNTHETIC RUBBER SO TREATED, FORMING THE SAME INTO A TEXTILE FIBER DRAFTING ELEMENT, AND VULCANIZING THE SAME. 